MongoDB:检查值是否为空或数组是否为空
问题描述：
我想匹配所有不包含公司"属性或公司"值为空或空数组的文档.
I would like to match all documents that don't contain the "Company" attribute or where the "Company" value is null or an empty array.
User.find({Company: {$in: [null, [] ]}}, function (err, users) {
if (err) { throw err; }
console.log(users.length);
}).then(function(doc) {
console.log("finish User Company");
});
答
您可以使用 $or 查询运算符，检查每个条件:
You could use the $or query operator with a check for each condition:
{
$or: [{
// Check about no Company key
Company: {
$exists: false
}
}, {
// Check for null
Company: null
}, {
// Check for empty array
Company: {
$size: 0
}
}]
}